The present invention concerns an electric motor-driven screw driving or drilling tool device with a planetary gear, comprising a ring gear and planet wheels mating with the ring gear, wherein the planet wheels are driven to roll on the ring gear and have axles which drive a drive shaft, and with a torque adjusting means, wherein the ring gear can be locked such that it is fixed relative to the housing via locking bodies which are pretensioned in a radially inward direction by springs, and the locking bodies can be displaced in a radial outward direction when a switch-off torque has been exceeded, such that the ring gear can rotate relative to the housing, and the drive shaft is no longer driven.
A screw driving tool device of this type is disclosed in EP 1 391 269 A2. The plurality of locking bodies of this conventional screw driving tool device are pressed radially inwardly into depressions in the ring gear via an inclined surface arrangement on a bearing ring. The bearing ring is axially pretensioned by helical springs. The inclined surface arrangement deflects this axial pretension into a radially inward component. In order to adjust the maximum torque, an adjusting ring and thereby also the bearing ring are rotated such that another inclination of the inclined surface arrangement cooperates with the locking bodies, to produce a different radial force component, wherein the balls displace the inclined surface arrangement and the bearing ring against the spring force. In order to adjust this maximum torque, the user must disadvantageously perform an adjusting motion against the spring force.
U.S. Pat. No. 4,448,098 discloses an electric motor-driven screw driving tool device, also comprising a planetary gear means and a torque adjusting means. This torque adjusting means has one single locking body which is pretensioned in a radially inward direction by a spring, and locks a ring gear such that it is fixed relative to the housing when the drive is coupled. The single locking body is pretensioned by a leaf spring which extends in an axial direction, wherein the pretension of the leaf spring can be adjusted by a slider which can also be moved in an axial direction for this purpose. The torque adjusting means therefore disadvantageously requires a large amount of space in the axial direction. Another disadvantage is that the ring gear of the conventional screw driving tool device can be fixed relative to the housing only by one single locking body which must therefore adopt and transmit correspondingly large clamping forces, leading to increased wear.
It is the underlying purpose of the present invention to improve a screw driving tool device of the above-mentioned type to facilitate handling thereof, reduce the required space, and increase the wear resistance.